Vergara, C.
Harper, 1958
Buku Teks
Ryan, John C., author
Sierra Club Books, 1999
Buku Teks
Bloomfield, Louis A., author
John Wiley & Sons, 2006
Buku Teks
edited by Dede Brouwer, Dorian de Haan
Foris Publications, 1987
Buku Teks
Natov, Roni, author
Routledge, 2006
Buku Teks